Surgical staplers have been used in the prior art to simultaneously make a longitudinal incision in tissue and apply lines of staples on opposing sides of the incision. Such instruments commonly include a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument includes a plurality of reciprocating wedges that, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
An example of a surgical stapler suitable for endoscopic applications is described in U.S. Patent Application Publication No. 2004/0232196, now U.S. Pat. No. 7,000,818, the disclosure of which is herein incorporated by reference in its entirety. In use, a clinician is able to close the jaw members of the stapler upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can then fire the surgical stapler, thereby severing and stapling the tissue. The simultaneous severing and stapling avoids complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever or staple.
Whenever a transection of tissue is across an area of varied tissue composition, it would be advantageous for the staples that are closest to the cut line to have one formed height that is less than the formed height of those staples that are farthest from the cut line. In practice, the rows of inside staples serve to provide a hemostatic barrier, while the outside rows of staples with larger formed heights provide a cinching effect where the tissue transitions from the tightly compressed hemostatic section to the non-compressed adjacent section. In other applications, it may be useful for the staples in a single line of staples to have differing formed heights.
U.S. Pat. Nos. 4,941,623 and 5,027,834 disclose surgical stapler and cartridge arrangements that employ staples that have different prong lengths to ultimately achieve lines of staples that have differing formed heights. Likewise, WO 2003/094747 A1 discloses a surgical stapler and cartridge that has six rows of staples wherein the outer two rows of staples comprise staples that are larger than the staples employed in the inner two rows and middle rows of staples. Thus, all of these approaches require the use of different sizes of staples in the same cartridge.
Consequently, a significant need exists for an improved cartridge for a stapling instrument that can form lines of staples that have differing formed heights without the need to employ different sizes of staples in the same cartridge.